Simon Cowell said attending tonight's world premiere of Harry Hill's X Factor spoof musical I Can't Sing! was like seeing his second baby born this year.

The music mogul - who last month became a father for the first time - is one of the show's financial backers, and his recent parenthood is reflected in its script.

Cowell, who walked the red carpet at the Palladium in London with girlfriend Lauren Silverman, said: "It's like my second baby this year, it feels like that.

"It's exciting, and I never thought I'd be in this spot. I don't know much about the West End or musicals but the very first time I saw the run through I really, really liked the show.

"And now I've seen the Twitter reaction to the previews and the people who've seen it really love it. So I'm thrilled."

The production, which stars Nigel Harman as a Cowell-like show boss, takes an affectionate swipe at a number of figures associated with the ITV show with characters based on Cheryl Cole - who is to return to the singing contest later this year - and Louis Walsh. Take That star Gary Barlow gets a nod with a dog named after him.

There have been some teething troubles with the show during the early days of its preview run at the theatre, with scheduled performances put back by a few days in order to sort out issues with the way it is staged.

And guests at the first preview reported that too was hit by a 50-minute interval, although producers are now understood to have got the delays under control as the show has bedded in.

But Cowell said: "It's a big production, that's why you have all the previews and you work everything out. But it worked out fine in the end. I've been to two of the shows and we're sure it's going to work tonight."

Harry Hill said he was confident about opening night. "I feel excited more than nervous," he insisted.

"We've run it now for four weeks and it's always gone really well, so, the law of averages..."

And he also promised he hadn't held back when mocking Cowell or any of the other judges. Hill said: "We never thought twice about it. We wrote what we wanted to write and he was always fine about. I'm not the sort of person who is nasty for the sake of being nasty."

Meanwhile, Cowell said he was delighted to have Cheryl Cole back as a judge for the 11th series of The X Factor. "I charmed her," he said.

He refused to reveal who else was joining him on the panel, but denied he had been in talks with Rihanna.

Cowell added: "Louis - I would love him to come back and do the show, it wouldn't be the same without him.

"Other people have different views, so we have to agree on it.

"But a lot of the stuff I've read about in the press... I haven't spoken to these people."